1. Field of the Invention
This invention relates to systems for dispensing foam material, and more particularly to systems which maintain the material under pressure with foaming gas in solution and which dispense the material/gas solution to form the foam.
2. Description of the Prior Art
The assignee of the present invention had developed methods and apparatus for dispensing high-performance sealants that are foamed in place, creating closed-cell foam seals that act as effective, long-lasting barriers against air, dust, vapor and fluids in various applications. The sealant may be any pumpable material, such as polyurethane, silicone or plastisol and is usually a curable polymeric sealant material which has a very high viscosity. Using this foam-in-place technology a gas that is inert to the sealant material is mixed with the sealant material under high pressure to dissolve the gas in a solution, and the solution is maintained under high pressure to prevent the gas from escaping or from prematurely foaming the material. The material/gas solution is then dispensed from a nozzle at atmospheric pressure, allowing the gas to come out of solution and foam the sealant material. This technology produces a foam without any chemical reaction, without any chemical blowing agent and without any volatiles. It allows for a reduction in the use of expensive materials such as polyurethanes and silicones and provides improved compressibility, resilience and reduced cure time.
It is difficult to successfully mix the low viscosity foaming gas with the highly viscous sealant material so as to achieve a uniform solution without creating undesirable heat and other problems. Many of these difficulties have been solved by using a bulk mixer and associated apparatus as described in U.S. Pat. No. 4,778,631. The mixing may be accomplished by a disk mixer that thoroughly mixes the low viscosity foaming gas into the high viscosity material. The mixer may be driven by a constant speed motor, which is monitored by a torque sensor. The mixing apparatus may also require a bulk melter for the material that is fed to the mixer, a cooling system with a supply of cooling fluid, and a pressurized supply of foaming gas including a pump. This apparatus is relatively large and bulky, and it is not portable, but it is advantageously used in large-scale production facilities to produce foam sealant which can be applied by robotic devices, replacing the old, labor-intensive manual method of applying die-cut gaskets. The apparatus uniformly blends the foaming gas with curable sealant materials to produce high-performance gaskets. Automated foam-in-place gasketing increases production, reduces labor and material costs, and improves quality through accurate and consistent gasket placement.
These highly desirable gasketing systems would also prove beneficial outside of the large-scale production facilities. For example, the foam-in-place gasketing material could be advantageously used on site at building installations, to provide high quality gaskets around windows and in other parts of building construction. The use of foam-in-place gasketing systems outside of large-scale production facilities, however, has been hindered by the requirements of the large mixing apparatus that is needed to produce the pressurized material/gas solution. In order to apply this foam sealant material on site, it would be necessary to supply a large mixing apparatus in close proximity to the location where the sealant was being applied. On most construction sites, the worker is moving from one location to another, for example, applying sealant material a various windows located throughout the site, and it would be impractical for the worker to move the large mixing apparatus with him in order to utilize foam-in-place sealant technology and to produce the improved sealing gaskets that this technology provides.